4,864 research outputs found
A DSMC investigation of gas flows in micro-channels with bends
Get PDFPressure-driven, implicit boundary conditions are implemented in an open source direct simulation Monte Carlo (DSMC) solver, and benchmarked against simple micro-channel flow cases found in the literature. DSMC simulations are then carried out of gas flows for varying degrees of rarefaction along micro-channels with both one and two ninety-degree bends. The results are compared to those from the equivalent straight micro-channel geometry. Away from the immediate bend regions, the pressure and Mach number profiles do not differ greatly from those in straight channels, indicating that there are no significant losses introduced when a bend is added to a micro-channel geometry. It is found that the inclusion of a bend in a micro-channel can increase the amount of mass that a channel can carry, and that adding a second bend produces a greater mass flux enhancement. This increase happens within a small range of Knudsen number (0.02 Knin 0.08). Velocity slip and shear stress profiles at the channel walls are presented for the Knudsen showing the largest mass flux enhancement
Penerapan Sistem Koordinasi Modular pada Desain Hunian Vertikal Apartemen TJ
No full textPenerapan Sistem Koordinasi Modular Bangunan Pada Desain Hunian Vertikal Apartemen TJ BAMBANG SUBEKTI, ALENCIA M. R., RAFIKA R. R., PETRA A. R., DESRIZAL GUNAWAN Jurusan Teknik Arsitektur, Fakultas Teknik Sipil dan Perencanaan Institut Teknologi Nasional Email : [email protected] ABSTRAK Kebutuhan masyarakat Bandung akan hunian semakin hari semakin meningkat. Alternatif pemenuhan kebutuhan tersebut adalah dengan membuat hunian vertikal. Untuk mempercepat pengadaan hunian vertikal tersebut salah satunya melalui metoda membangun dengan menggunakan metoda fabrikasi. Pendekatan pembangunan dengan komponen fabrikasi menuntut perancangan dengan sistem koordinasi modular yang bersifat berulang, baik pada modul dasar yang direncanakan juga pada komponen yang telah tersedia di pasaran. Penelitian ini bertujuan untuk mengamati dan meneliti penggunaan sistem koordinasi modular pada perancangan Apartemen TJ sebagai kasus studi. Metode penelitian yang digunakan adalah analisis deskriptif dengan menjelaskan kesesuaian antara perancangan modul dengan berbagai komponen yang digunakan. Hasil dari penelitian ini adalah bahwa Apartemen TJ menggunakan sistem modular pada komponen kolom, dinding horizontal, sebagian dinding vertikal, bukaan, jendela, langit-langit, dan parkir. Kata kunci : hunian vertikal, koordinasi modular ABSTRACT The needs of people in Bandung about residence is constantly increasing. Alternative meeting those needs is to create a vertical housing. To expedite the procurement of vertical housing of one of them by the method of building using the method of fabrication. Development approach to fabricating components require design with modular coordination system that is repeated , either on the basis of the planned modules and also on the components that have been available on the market . This study aims to observe and examine the use of modular coordination system on designing Apartment TJ as a case study . The method used is descriptive analysis to explain the compatibility between design modules with different components used . Results of this study was to know that the Apartment TJ uses a modular system of components columns, horizontal walls, partially vertical walls, openings, windows, ceilings, and parking
Will biological agents supplant systemic glucocorticoids as the first-line treatment for thyroid-associated ophthalmopathy?
No full textIn this article, the two authors present their opposing points of view concerning the likelihood that glucocorticoids will be replaced by newly developed biological agents in the treatment of active, moderate-to-severe thyroid-associated ophthalmopathy (TAO). TAO is a vexing, disfiguring and potentially blinding autoimmune manifestation of thyroid autoimmunity. One author expresses the opinion that steroids are nonspecific, frequently fail to improve the disease and can cause sometimes serious side effects. He suggests that glucocorticoids should be replaced as soon as possible by more specific and safer drugs, once they become available. The most promising of these are biological agents. The other author argues that glucocorticoids are proven effective and are unlikely to be replaced by biologicals. He reasons that while they may not uniformly result in optimal benefit, they have been proven effective in many reports. He remains open minded about alternative therapies such as biologicals but remains skeptical that they will replace steroids as the first-line therapy for active, moderate-to-severe TAO without head-to-head comparative clinical trials demonstrating superiority. Despite these very different points of view, both authors are optimistic about the availability of improved medical therapies for TAO, either as single agents or in combination. Further, both agree that better treatment options are needed to improve the care of our patients with active moderate-to-severe TAO
Anode and cathode arc root movement during contact opening at high current
Get PDFThis paper presents experimental research into the behavior of short circuit break arcs ignited between opening contacts. The investigation is applied to arc chamber geometries commonly used in miniature circuit breakers (MCB). The movement of the anode and cathode roots are individually plotted from optical data, allowing the relative motion to be compared. The effect of a range of MCB configurations on the arc root motion has been investigated. The experiment was configured so that the fixed contact was always the cathode. The results show that the two are roots do not move away from the contact region simultaneously. Often the cathode root moved off the fixed contact and away from the contact region before the anode root commutated from the moving contact. The delay in anode root commutation leads to a delayed cathode root movement. These events are explained in terms of arc root emission processes
The value of silence
No full textThis is an electronic version of the article published in Theatre Journal, 54(1):85-94, 2002 March. The published article is available at http://muse.jhu.edu/journals/theatre_journal/v054/54.1eng.pdfEng, David L.The Value of Silence.Theatre Journal, 54,(1):85-94, 2002.DOI: 10.1353/tj.2002.000
Growth of vertically aligned bamboo-shaped carbon nanotubes
No full textThe vertically aligned uniformed carbon nanotubes (CNTs) oil a large area of Ni deposited Si substrates were grown by thermal chemical vapor deposition using C2H2 gas. The diameter of CNTs is as small as about 60 nm and the length is about 50 mum. High-resolution TEM analysis reveals that the CNTs have the uniformed multi-walls, the bamboo structure, and the sharp closed tip. The CNTs have multi-walls with good crystallinity and there are some defects on the wall surface. The base growth model is suitable to bamboo-shaped CNTs using thermal chemical vapor deposition
Capturing the Knudsen layer in continuum-fluid models of non-equilibrium gas flows
No full textIn hypersonic aerodynamics and microflow device design, the momentum and energy fluxes to solid surfaces are often of critical importance. However, these depend on the characteristics of the Knudsen layer - the region of local non-equilibrium existing up to one or two molecular mean free paths from the wall in any gas flow near a surface. While the Knudsen layer has been investigated extensively using kinetic theory, the ability to capture it within a continuum-fluid formulation (in conjunction with slip boundary conditions) suitable for current computational fluid dynamics toolboxes would offer distinct and practical computational advantages
Some consequences of non-local-equilibrium in hypersonic aerodynamic flows
No full textIn simulating high-speed, high-altitude aerodynamics it is important to be able to capture physical phenomena that are due to the non-local-equilibrium nature of the rarefied gas flow (this is in addition to any effects due to dissociation, ionisation and energy partition in diatomic molecules). The physical effects of the gas rarefaction can be particularly important close to any solid surface, where they have implications for the heat transfer and mechanical stresses experienced by the surface, and hence on the design of the leading edges and control surfaces of aerodynamic vehicles
The nonlinear hydroelastic behaviour of flexible walls
No full textA computational model is developed to study the hydroelastic response of simple panels and compliant walls to a uniform flow. Numerical experiments are presented which simulate the history of hydroelastically unstable disturbances as they evolve from amplitudes that may be treated by linear theory to amplitudes for which non-linearity in both the wall and flow cannot be neglected. The method is first applied to simple unsupported flexible panels. Unstable deformations of these panels are seen to be dominated by the fundamental mode. When some panel damping is incorporated, the panel ultimately settles into a static buckled state; however, this long-time response may be preceded by sustained nonlinear oscillations. The amplitudes and frequencies of these oscillations are characterized as a function of wail and flow properties. The method is then used to study a compliant wall comprising a spring-backed flexible plate. For low levels of wall damping, linearly unstable waves evolve into a complex limit-cycle Butter-type response. For high levels of damping small-amplitude unstable disturbances evolve into saturated nonlinear divergence waves that have sharp peaks and shallow troughs. These have much slower downstream wave travel than small-amplitude growing divergence waves. Features of the simulated waves and their dependence on the freestream how show good qualitative agreement with experimentally measured nonlinear divergence waves. The characteristic waveform of the nonlinear divergence waves is shown to be attributable to the hydrodynamic stiffness pressure field generated by large-amplitude disturbances. (C) 1997 Academic Press Limited
An engineering approach to modelling of dynamic insulation using ESP-r
No full textThe use of Dynamic Insulation (DI) can enable recovery of conduction heat loss through a building envelope. This is an active process that allows air to move through the fabric against the temperature gradient. Additionally it promises better indoor air quality, primarily due to filtration properties of the construction material [11]. This paper is concerned with quantifying the energy savings and enhancement of human comfort if this technology is integrated into a building. To ascertain the impact of the technology on whole-building performance, it is necessary to undertake detailed dynamic modelling. A suitable building and plant simulation computer tool (ESP-r) was employed to do this. A technique for modelling the dynamic insulation was developed and validated against known analytical solutions. A full-size test house was then simulated, in the UK climate, with and without DI. Comparative results show that better thermal comfort and energy savings are possible with the use of DI. The results obtained have been translated into suggestions for best practice
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